Frederick g



F. G. KEYES.

CRUCIBLE.

APPLICATION FILED OCTJH 1915.

Patented Oct. 14, 1919.

UNTTED' sTATEs PATENT OFFICE.

FREDERICK G. KEYES, OF HOBOKEN, NEW JERSEY, ASSIGNOR TO COOPER HEWITT ELECTRIC COMPANY, OF HOBOK'EN, NEW JERSEY, A CORPORATION 0F NEW JER- SEY.

CRUCIBLE.

Specification of Letters Patent.

. Patented 0015.14, 1919.

Application led October 28, 1915. Serial No.A 58,826.

To all Mahomet may concern Be it known that I, FREDERICK Gr. KEYES, a citizen of the United States, and resldent of Hoboken, county of Hudson, State of New Jersey, have invented certain new and useful Im rovements in Crucibles, of which the following is a specification.

In preparing crucibles of tungsten, I may make use of a graphite mold and a core so adjusted to the mold as to leave between it and the inner wall of the mold a space for the formation o'f the crucible. Into this space pure tungsten powder is packed and the core subsequently removed. To facllitate the removal of the core, the interior of the mold and the Core are preferabl made conical in shape. It is found that t e shell of tungsten thus formed is not liable to disintegration under ordinary handling. It is sometimes of advantage to mix a little tungsten with one or two per Cent. of Ni() or 20% of molybdenum oXid, MOO, before prepari the reduced metallic powder. This addltion of a lower melting metal (in case molybdenum oxid is added) makes the Crucible Contract slightly, thus facilltating its withdrawal from the mold after beingv fired. The firing is accomplished by merely bringing the Crucible rapidly to about 2000o in a carbon resistance furnace.

After removing the sintered and porous metal cup from the mold, it is taken out, filled with IN2()5 and mounted on a pedestal within a resistance tube graphite furnace. The temperature of the Crucible is gradually raised until the oXid melts, whereupon the poroils walls immediately absorb it like a sponge. Carbon monoxid is now introduced and the temperature at the same time raised. Under these conditions the molten oXid ills the pores'of the Crucible and is there quickly reduced with the result that a perfectly tight and homogeneous vessel of tungsten is produced. In the case of a tall Crucible, it is sometimes necessary to refill and repeat the above described process. In the accompanying drawings, I have illustrated in Figure l, which is sectional, the mold and its core, and the packing of tungsten between the mold and the core; in Fig. 2 I have shown the details of a Carbon resistance furnace suited to assist in carrying the process to completion; in Fig. 3 a modication appears and in Fig. 4 a fully completed tungsten Crucible is shown.

Referring now more particularly to the first ligure of the drawing, 1, is the graphite mold having a coneshaped interior, as shown, and, 2, is a Core also having a coniv cal shape, and capable of being set into the mold, leaving a space lfor the reception of pure tungsten or tungsten mixed with Ni or Mo'. For purposes of manipulation, the core 2 is provided with a handle, 36. Into the space thus left between the Core and the mold pure tungsten or the compound mentioned above is tamped and the core then removed, as already described. Afterward the tungsten material in the form of a crucible may be withdrawn, in which case it will appear as shown at 3 in Figs. 1 and 4.

-The crucible thus formed, and identified herein as the element 3, may then be mounted upon a standard or pedestal, 4, which is of carbon and is hollow at its lower end to admit nitrogen or other neutral gas through a pipe 5. Approximately midway of the standard 4 is a cone shaped flange 6, the surface of which forms a cone it with the end of a resistor tube, 7. The resistor consists of a tubular helix of graphite, and constitutes the heating element of a carbon furnace. Massive clamps, 8 and 9, grip, respectively, the upper and lower extremities of the resistor, with which clamps are joined pipes 10 and 11, which serve the double purpose of admitting water for cooling the extremities of the resistor and of conveying electric current to and from the resistor foll heating the same. The source (not shown) from which the electric current is derived is an .alternating current source connected with the circuit 12, 13, and acting through a, transformer, 14, 15, 16 and 17, to pass current through conductors 18, 19, and 10 and 11, and the resistor 7. Pipes or tubes 20 and 21, serve as exit pipes *for the cooling water, after it'has passed through the hollow clamps 8 and 9.

The whole apparatus here described is inclosed within an iron vessel, 22, and the pipes 10, 11, 20 and 21 pass into and out of a ca 23, on said vessel, through insulating bushmgs, 24 and 25.

The tube 7 is internally taper bored at its top to receive a carbon adapter, 26, provided at its top with a mica window, 27, for observation purposes.

A small space is left outside the resistor 7 and two concentric graphite tubes, 28 and -the pores of t 29, are placed around the resistor with insulating material, 30, between them. This constitutes lan insulation shield around the resistor.

These tubes are supported on the connector clamp 9 with an interposed Hat ring, 31, of asbestos board or other ood insulating material between them. t the top a similar ring, 32, is placed between the connector clamp 8 and the tops of the concentric tubes 28 and 29. l

At the bottom of the vessel 22 is a reduced extension, 33, thereof to the bottom of which is applied a screw cap, 34, into which the tube 5 already mentioned enters at `such a point as to communicate with the hollow lower end of the standard or pedestal 4C. A neutral gas such as nitrogen, introduced through the tube or pipe 5, may nd entrance to the space inside the heater 7 by way of openings 35, 35, in the conical liange, 6.

lt is now evident that the screw Cap 34 may be removed and with it the pipe 5, and the standard or pedestal 4L, so that the Crucible 3 may be put in place outside thefurnace and any desired materials can be placed inside the Crucible to be later subjected to heat when the apparatus is put inside the furnace, as shown in Fig. 2.

Generally, the Crucible 3 having been mounted on the standard or pedestal 4:, is filled with WQQ., or with lVOZ. As the temperature gradually rises during -the operation of the furnace thevoXid within the crucible is melted, whereupon the walls of the Crucible absorb it like a sponge. On introducing Carbon-monoxid and continuing to raise the tem erature, the molten oXid lls Ille Crucible and is quickly reduced, 'the result being that a perfectly tight and homogeneous vessel of tungsten is prol sten Crucible which conslsts 1n forming a poduced.

The Carbon monoxid' may be introduced through the tube 5, or in any other convenient way.

In Fig. 3 I show a rod of porous tungsten dipped into the same. materials inside the Crucible 3 as have already been described. The materials, however, Aare here shown as in a molten state and the rod will absorb, by a Y single operation or by repeatedoperations, the molten oXids and will, in its final shape, become a rod, bar, or ingot, of pure tungsten.

It will be observed that the walls of the iron Jr'urnace 22 are remote from the interior heated portion and are, therefore, little likely to be injuriously affected by the opgeraete eration of the development of heat in the resistor. In other words, the actualvheating space is limited, thus concentrating the heat at or near the point where it needs to be applied and preventing the useless dissipation of the heat.

The carbon monoXid may be conveniently generated by permitting the nitrogen to bub- -ble through water prevlous to its entering the furnace.' rllhe small amount of water vapor thus carried into the heated zone o1E the furnace is immediately converted into carbon-monoxid and hydrogen, thus automatically furnishing a sufficient amount of reducing gas which suiices in the present instance. lf it is desired to avoid the presence of hydrogen it is convenient to pass air through a quartz tube containing carbon maintained at about 1000". This quartz tube heater is conveniently made up by winding a platinum wire or ribbon about the outside, and providing suitable heat insulation. rl`he air on passing over the heated graphite or carbon emerges from the other end of the furnace as carbon-monoxid, carbon-dioxid and nitrogen, the oxygen of they air being used up to form the carbon oXids. llt is known that at a-thousand degrees, oxygen will exist in Contact with carbon, as carbon-monoxid and carbon-dioXid, the proportion` of carbon dioXid being less, the higher the temperature. Consequently, when the gas mixture reaches the highly heated graphite tube furnace, practically nothing but carbon-monoxid exists.

I claim as my invention:

1. The method of preparing a pure tungsten crucible which consists in forming a porous tungsten Cup of Crucible shape, {illing the same with an oxid of tungsten and heating the Crucible until the oXid melts.

2. The method of preparing a pure tungrous tungsten cup of Crucible shape, filling the same with an oXid of tungsten, raising the temperature, whereby the' molten oXid fills the pores of the Crucible, introducing reducing gas and forming a perfectly tight and homogeneous vessel of pure tungsten. i

Signed at New York in the county of New York and State of New York this 26th day of October, A. D. 1915.

FREDERICK Gr. KEYES. Witnesses:

HAROLD B. WooDwARD, Trios. H. BROWN. 

